1. Field of the Invention
This invention relates generally to X-ray generator cooling apparatus and is concerned more particularly with a fluid-cooled X-ray generator system having means for purging foreign gaseous matter from the fluid.
2. Discussion of the Prior Art
A conventional X-ray generator may include a radiation shielded housing for enclosing an X-ray tube having an envelope wherein an electron emitting cathode is disposed for beaming electrons onto a spaced anode target with sufficient energy to generate X-rays. Generally, the housing is provided with a pair of mutually insulated connectors for feeding a selected electron emission current through the cathode and for applying appropriately high electron beaming voltages between the cathode and anode electrodes of the tube. Also, since a large portion of the electron energy beamed from the cathode onto the anode target is converted into heat, the housing may be connected to a pressurized source of dielectric coolant fluid, such as oil, for example, for circulating the fluid through the housing to carry heat away from the tube.
The fluid circulated through the housing is required to have suitable high dielectric properties for withstanding the high voltages applied between the cathode and anode electrodes of the X-ray tube. However, it has been found that bubbles or larger volumes of foreign gaseous matter, such as air, for example, may become immersed in the dielectric coolant fluid and reduce the dielectric properties of the fluid. The air can be introduced into the coolant fluid during installation, repair, or in general, whenever the fluid coolant apparatus is disconnected from the housing. Furthermore, it is possible that air may be drawn into the coolant oil due to differences in vertical heights causing a head pressure in portions of the coolant apparatus. Also, air may seep into the coolant fluid at joints or other connections during extended idle periods when air buildup can occur. In addition, X-rays in passage through the dielectric fluid generate a gas, such as hydrogen, for example, which also may be trapped in the fluid within the housing. Once inside the housing, the air or other foreign gaseous matter may migrate to critical portions of the housing, such as between the electrical connectors for the tube, for example, where electrical arcing may result and possibly damage the tube.